In the past, a landmark display for a building, etc.; an advertisement display; recreational facility information or congestion situation of an amusement park, etc.; description of an item in a store window; explanation of an exhibit in a museum or public show, etc. has been performed using “visual information,” such as characters, graphic symbols, etc., written on “information presentation signs,” such as paper, banners, billboards, plates, etc.
However, when someone wants to look for a specific information notice in an environment with a lot of information presentation signs, a problem occurs in that the information notice is not conspicuous with the surrounding information presentation signs. For example, when product A and product B are adjacently exhibited at a store, the item description of product A may be mistaken for the item description of product B.
Consequently, with the use of information transmission by optical space transmission as in the conventional prior art 1 (reference to Japanese Laid-Open Patent Application No. 2001-245253 titled “IMAGING DEVICE”/Page 2, Page 5, FIG. 1 and FIG. 10), the information presentation for a product and the corresponding relationship of its presentation information can be clarified as well as erroneous assumption of information comprehension can be eliminated. Furthermore, an information reception device which also considers information integrity has been devised.
Specifically, this conventional prior art 1 discloses time-oriented image capturing with an electronic still camera and memorization of an optical tag unit mounted near a product arranged in a showcase. The data is recognized as information subjected to optical modulation from the time-oriented optical variation of the optical tag unit which resides in that stored image. Afterwards, the data about that particular product is extracted from this information subjected to optical modulation. The same extracted information is displayed superimposed on the captured image. However, in this conventional prior art 1, there exists a technological problem in that extraction of the optical tag unit information cannot be performed accurately, for example, when there is a light source (for example, disturbance light, such as flicker of a fluorescent light) in the vicinity which is prone to optical variations by the same pattern as the optical variation pattern of a blinking optical tag unit.
In view of such a problem, as in the conventional prior art 2 (reference to Japanese Laid-Open Patent Application No. 2003-179556 titled “INFORMATION TRANSMISSION METHOD, INFORMATION TRANSMISSION SYSTEM, IMAGING APPARATUS AND INFORMATION TRANSMISSION METHOD”/Pages 7˜8 and FIGS. 7˜10), an information reception device, information transmission system and information transmission method has been devised which always extracts information properly and avoids adverse effect produced by disturbance light.
Specifically, this conventional prior art 2 uses a light reception unit having an image sensor, such as a CCD (Charge-Coupled Device), etc. An optical variation from a light-emitting unit (equivalent to the optical tag unit in the conventional prior art 1) is detected which exists in the capture angle (also referred to as the field of view) of the image sensor. While binarization of a bit pattern sequence is being carried out by converting the variation level of that optical variation into modulation information, the operation determines whether or not any bit pattern sequence coincides with previously prepared binarized bit pattern sequences which did not correlate reciprocally. Subsequently, by generating a two-value logic signal (1/0) based on that determination result, the transmitted information from the light emitting unit is reproduced. In this manner, the light generation pattern of this light emitting unit is made unique and the effect of disturbance light is decreased.
However, in the conventional prior art 2, although the adverse influence by disturbance light can be avoided, there is a problem with wastefulness in processing an image.
Basically, in the conventional prior art 2, even if carrying out the above-mentioned binarization processing, logic processing of a bit pattern sequence after binarization processing, etc., a “partial read-out” is performed from an image within the capture angle of the image sensor and the read-out area is shifted for every cycle. These processes are unchanging by being targeted at all of the pixels of an image frame outputted from an image sensor. In other words, this method is none other than performing detection and capture of the point light source pertaining to all regions of an image within the capture angle of the image sensor. Therefore, as explained below, wasteful processing cannot be refused.
Assuming that the total number of pixels within the capture angle of the image sensor (full dots) is 1280×960 dots and supposing that a partial read-out of 320×240 dots is possible for this image sensor, the above-mentioned conventional prior art 2 binarization processing, logic processing of a bit pattern sequence after binarization processing, etc. will be performed for each area in which an image of 1280×960 dots is divided into 4×4 blocks. In this case, since one processing is performed applying to the pixels of 320×240 dots for one area, if observing only one processing, the processing load is definitely less. However, the visual recognition size of the point light source located at a distance, namely, the point light source of the light emitting unit, is considerably small. In a lot of cases, this level is completely obtained in one divided area. Thus, processing is inefficient for the other divided areas which do not include a point light source.